See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Concept: The heat of combustion of a molecule is a measure of the energy released when it burns completely. For isomers (which have the same molecular formula and thus the same combustion products), the isomer with the HIGHER heat of combustion has MORE energy stored in it (higher potential energy / higher enthalpy content), meaning it is LESS stable. Conversely, the isomer with the LOWER heat of combustion is MORE stable because it sits at a lower energy level. Reasoning: - Isomer x has a heat of combustion of 17 kJ/mol. - Isomer y has a heat of combustion of 12 kJ/mol. - Since isomer x releases more energy upon combustion (17 > 12), isomer x has more stored (potential) energy and is therefore LESS stable than isomer y. - The difference in stability is 17 - 12 = 5 kJ/mol. - Therefore, isomer x is 5 kJ/mol less stable than isomer y. Why other options fail: (a) 'Isomer x is 5 kJ/mol more stable' — Incorrect. Higher heat of combustion means less stable, not more stable. (b) 'Isomer y is 5 kJ/mol less stable' — Incorrect. Isomer y has lower heat of combustion, so it is MORE stable, not less. (c) 'Isomer y has 5 kJ/mol more potential energy' — Incorrect. Isomer x has more potential energy since it releases more energy on combustion. (d) 'Isomer x is 5 kJ/mol less stable' — Correct. Isomer x has higher heat of combustion, so it has higher potential energy and is 5 kJ/mol less stable than isomer y. Therefore, the correct answer is D.